1. Technical Field
The present invention relates to wireless communications and, more particularly, to integrated circuit based voltage regulators.
2. Related Art
Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards, including, but not limited to, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), and/or variations thereof.
Depending on the type of wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, etc., communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of a plurality of radio frequency (RF) carriers of the wireless communication system) and communicate over that channel(s). For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via a public switched telephone network (PSTN), via the Internet, and/or via some other wide area network.
Each wireless communication device includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for in-home and/or in-building wireless communication networks, RF modem, etc.). As is known, the transmitter includes a data modulation stage, one or more intermediate frequency stages, and a power amplifier stage. The data modulation stage converts raw data into baseband signals in accordance with the particular wireless communication standard. The one or more intermediate frequency stages mix the baseband signals with one or more local oscillations to produce RF signals. The power amplifier stage amplifies the RF signals prior to transmission via an antenna.
Typically, the data modulation stage is implemented on a baseband processor chip, while the intermediate frequency (IF) stages and power amplifier stage are implemented on a separate radio processor chip. Historically, radio integrated circuits have been designed using bipolar circuitry, allowing for large signal swings and linear transmitter component behavior. Therefore, many legacy baseband processors employ analog interfaces that communicate analog signals to and from the radio processor.
Typically, a portable device includes a regulator coupled to a power source for providing a regulated and constant voltage for an associated circuit. For example, a regulator output may be used as a supply voltage for a circuit within an integrated circuit. Additionally, a portable device includes a rechargeable battery that is periodically charged either while the portable device is on or off. One problem with such portable devices, however, is that the typical regulator is not always able to provide a regulated voltage within a specified tolerance because of substantial variations in an input voltage to the regulator. This problem is especially acute for low voltage applications.
For example, the voltage across a charging battery that is connected to circuitry for a portable device may be substantially higher than under ordinary conditions while charging. The regulator may therefore provide a voltage that is above its specified maximum for certain applications including low voltage applications. Moreover, regulation modules within integrated circuits are operable only a limited drop in ripple to provide clean signals for audio and other applications. For example, regulator may provide a 98 reduction in ripple which may not be enough if the input ripple is large. What is needed, therefore, is a regulator that is operable to provide a specified regulated output voltage despite variations in supply due to the charge levels of an associated battery.